Conventional beam pumping units have long been the mainstream mechanical equipment for worldwide oil production. The conventional beam pumping units adopt a four-bar linkage mechanism and have advantages such as a reasonable velocity curve and decent reliability. However, there are several disadvantages including large peak torque, low mechanical efficiency, poor balancing, high manufacturing costs, and high energy consumption, which prevent further improvement of the oil production efficiency and cost efficiency. For example, in the patent titled “Beam Balance Block and Tackle Pumping Unit”, published on Aug. 13, 2014 by the State Intellectual Property Office of the People's Republic of China with application number 201410239831.4, a pulling wire rope from an output drum passes through a guide wheel first, and is then folded back to pass through a movable pulley from the outside of a horsehead, that is, from the curved side of the horsehead, and is finally connected to a damping extension spring on the ground. This wiring method of the pulling wire rope has the following defects: 1. The pulling wire rope passes through an additional guide wheel which increases the number of times the pulling wire rope is bent, which in turn affects the service life of the pulling wire rope. 2. When the guide wheel is lined up with the movable pulley on the horsehead perpendicularly to the ground, and the pulling wire rope is tangent to both wheels, the pulling wire rope can no longer pull the horsehead downward. Therefore, a sucker rod does not have enough stroke length. Experiments have proved that this design is not practical.